1. Field of the Invention
The present invention generally relates to an optical unit for projecting an image. More particularly, but not exclusively, the present invention relates to a tool which includes an optical unit for projecting an image of a scale which permits the tool user to complete adjustments of the tool from a more ergonomically advantageous position without the introduction of visual parallax error.
2. Discussion
Various tools are used in woodworking and metal forming to efficiently and accurately shape workpieces to desired dimensions and surface qualities. Such tools often include a workpiece forming element such as a bit, cutting blade, or the like, which is adjustable relative to the workpiece. For example, the workpiece forming element, in many instances, is carried by a movable component which is adjustable relative to the workpiece or relative to a base plate or platen upon which the workpiece may be supported. The significant majority of workpiece forming applications require quick and accurate adjustment of the workpiece forming element relative to the workpiece in order to obtain desired results.
A wood planing machine is one example of such a tool in which a workpiece forming element is adjustable relative to a workpiece. A conventional planing machine is used for the surface planing of boards and typically includes one or more rotatably mounted cutting blades attached to a vertically movable carriage assembly. In a typical wood surface planer, a selectively adjustable workpiece opening is defined between the carriage assembly and a workpiece support surface. The cutting blades are carried by the carriage assembly so as to be exposed adjacent to the workpiece opening. Generally, the carriage assembly is movably mounted to a plurality of support columns for movement with respect to the workpiece support surface, thereby permitting adjustment of the vertical dimension of the workpiece opening for selectively determining the amount of material to be removed from the workpiece and resultantly the ultimate thickness of the workpiece.
Multiple passes of the workpiece through the workpiece opening are often necessary to obtain the desired thickness and surface quality. Through adjustment of the carriage assembly relative to the support surface, the amount of material removed during a single pass can be varied. A pointer is typically fixed for movement with the carriage assembly and cooperates with a scale carried by the frame for visually indicating the desired thickness of the workpiece. As with other woodworking and metal forming operations, it is highly desirable that a planing machine accomplish workpiece preparation within precise tolerances, high surface quality, and with a significant degree of reproducible results.
While many commercially successful tools, including but not limited to known surface planers, are available which include an adjustable workpiece forming element adapted to be advanced relative to a workpiece and a scale and cooperating pointer for identifying the relative location of the workpiece forming element and the workpiece, all are subject to improvement. For example, such known tools require the user to accurately align his or her line of sight horizontally with the pointer in order to avoid the introduction of visual parallax error. This typically requires the user to bend or stoop to a position in which comfort is compromised and operation of the machine is hindered. This motion is particularly taxing on the user where repetitive adjustment is required. As a result, the quality of the forming operation is often adversely affected.